Activitypub is far too heavy. It literally requires a cryptographic exchange which makes a static setup for Activitypub infeasible. All activitypub based communication requires a big complex, fragile, exploitable dynamic backend on both sides that require ongoing mantainence.

RSS/Atom + Indieweb MF2/webmention is the way to go. It can be implemented by a static site with no moving parts to break.